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Journal of Rare Earths 2022年第1期40卷 34-40页

作者： Liubin Zheng Yanan Zhu Zengyuan Pang Mingqiao Ge College of Textile Science and Engineering Jiangnan UniversityWuxi 214122China Key Laboratory of Eco-Textiles Ministry of EducationJiangnan UniversityWuxi 214122China

In order to improve the red luminescent properties,Sr_(2)MgSi_(2)O_(7):Eu^(2+),Dy^(3+)was selected as a blue persistent luminescent donor phosphor,while light conversion agent was utilized to tune the persistent luminescent spectra from blue to red.Composite red luminescent material Sr_(2)MgSi_(2)O_(7):Eu^(2+),Dy^(3+)/light conversion agent(SMED/LCA)was fabricated with light conversion agent and Sr_(2)MgSi_(2)O_(7):Eu^(2+),Dy^(3+)at a certain mass ratio.SiO_(2)(Al2 O_(3) or MgF2)were coated on the surface of SMED/LCA through heterogeneous deposition method.The structural and optical characteristics of the resulting samples were launched in terms of X-ray diffraction and emission spectrum as well as afterglow brightness.The results demonstrate that the emission spectrum exhibits two emission bands,and the peaks are located at around 470 and 615 nm.SiO_(2),Al_(2)O_(3) and MgF_(2) are coated on the surface of SMED/LCA like a protective shell to maintain its stability and luminescent properties,the afterglow initial brightness is still up to 0.37 cd/m^(2) and the afterglow color purity calculated from CIE color coordinates is basically unchanged.

关键词： Sr_(2)MgSi_(2)O_(7):Eu^(2+),Dy^(3+) Light conversion agent Stability multilayer structure Composite material Rare earths

The effect of multilayer structure on magnetic properties of FePt thin films

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Acta Metallurgica Sinica(English Letters) 2009年第1期22卷 22-26页

作者： Kaifeng DONG Xiaofei YANG Junbing YAN Weiming CHENG Xiaomin CHENG Department of Electronic Science ＆： Technology Huazhong University of Science ＆ TechnologyWuhan 430074 China

The Fe/Pt multilayer films with different structures were deposited by RF magnetron sputtering on glass substrates, and the L10-FePt films were obtained after the asdeposited samples were subjected to vacuum annealing at various temperatures. Results show that the Fe/Pt multilayer structure can effectively reduce the ordering temperature of FePt film, and the in-plane coercivity of [Fe （5.2 nm）/Pt （5.2 nm）]7 multilayers can reach 161.2 kA/m after annealed at 350℃ for 30 min. When Fe and Pt layer thickness is equal, the coercivity of the film is the largest. On the other hand, the different Fe-Pt crystalline phases such as Fe3Pt and FePt3 phases are formed after annealing when the thickness ratio of Fe/Pt deviates from 1 after annealing. When Fe and Pt have the same thickness, the thinner single layer gets the lower ordering temperature and the larger coercivity.

关键词： L10-FePt thin films multilayer structure Coercivity Ordering temperature

Experimental verification of the detect interlaminar damage of a interface wave method to metal multilayer structure

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Frontiers of Mechanical Engineering 2015年第4期10卷 380-391页

作者： Bing LI Xu GENG Tong LU Lei QIANG Minghang LI State Key Laboratory for Manufacturing Systems Engineering Xi'anJiaotong University Xi'an 710049 China

The interface wave traveling along the bound- ary of two materials has been studied for nearly a century. However, experiments, engineering applications, and interface wave applications to the non-destructive inspec- tion of interlaminar composite have developed slowly. In this research, an experiment that applies Stoneley waves （a type of interfacial wave between two solid half-spaces） is implemented to detect the damage in a multilayer structure. The feasibility of this method is also verified. First, the wave velocity and wave structure of Stoneley waves at a perfectly bonded aluminum-steel interface are obtained by solving the Stoneley wave dispersion equation of two elastic half-spaces. Thereafter, an experiment is conducted to measure the Stoneley wave velocity of an aluminum- steel laminated beam and to locate interlaminar cracks by referring to the Stoneley wave velocity and echo wave time. Results indicate that the location error is less than 2%. Therefore, Stoneley waves show great potential as a non-destructive inspection method of a multilayer structure.

关键词： interface waves Stoneley waves interlaminardamage multilayer structure crack localization

Ultrahigh energy storage performance realized in AgNbO_(3)-based antiferroelectric materials via multiscale engineering

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Journal of Advanced Ceramics 2023年第6期12卷 1166-1177页

作者： Mingyuan Zhao Jing Wang Ji Zhang Li-Feng Zhu Lei Zhao Key Laboratory of High-Precision Computation and Application of Quantum Field Theory of Hebei Province College of Physics Science&TechnologyHebei UniversityBaoding 071002China State Key Laboratory of Mechanics and Control of Mechanical structures College of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China School of Materials Science and Engineering Nanjing University of Science&TechnologyNanjing 210094China School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China

Antiferroelectric(AFE)materials are promising for the applications in advanced high-power electric and electronic devices.Among them,AgNbO_(3)(AN)-based ceramics have gained considerable attention due to their excellent energy storage performance.Herein,multiscale synergistic modulation is proposed to improve the energy storage performance of AN-based materials,whereby the multilayer structure is employed to improve the breakdown strength(Eb),and Sm/Ta doping is utilized to enhance the AFE stability.As a result,ultrahigh recoverable energy storage density(Wrec)up to 15.0 J·cm^(-3) and energy efficiency of 82.8%are obtained at 1500 kV·cm^(-3) in Sm/Ta co-doped AN multilayer ceramic capacitor(MLCC),which are superior to those of the state-of-the-art AN-based ceramic capacitor.Moreover,the discharge energy density(Wa)in direct-current charge-discharge performance reaches 9.1 J·cm^(-3),which is superior to that of the reported lead-free energy storage systems.The synergistic design of composition and multilayer structure provides an applicable method to optimize the energy storage performance in all dielectric energy storage systems.

关键词： antiferroelectric(AFE) AgNbO_(3)(AN)-based ceramics energy storage multilayer structure

Multi-attribute wearable pressure sensor based on multilayered modulation with high constant sensitivity over a wide range

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Nano Research 2023年第5期16卷 7583-7592页

作者： Ning Li Song Gao Yang Li Jianwen Liu Wenhao Song Guozhen Shen School of Information Science and Engineering University of JinanJinan 250022China Shandong Provincial Key Laboratory of Network Based Intelligent Computing University of JinanJinan 250022China School of Integrated Circuits and Electronics Beijing Institute of TechnologyBeijing 100081China School of Aeronautical and Astronautical Engineering Purdue University West LafayetteIN 47907USA

Flexible pressure sensors capable of monitoring diverse physiological signals and body movements have garnered tremendous attention in wearable electronic devices.Thereinto,high constant sensitivity over a wide pressure range combined with breathability,biocompatibility,biodegradability is pivotal for manufacturing of reliable pressure sensors in practical sensing applications.In this work,inspired by the multilayered structure of skin epidermis,we propose and demonstrate a multi-attribute wearable piezoresistive pressure sensor consisting of multilayered gradient conductive poly(ε-caprolactone)nanofiber membranes composites.In response to externally applied pressure,a layer-by-layer current path is activated inside the multilayered membranes composites,leading to the most salient sensing performance of high constant sensitivity of 33.955 kPa^(−1) within the pressure range of 0–80 kPa.The proposed pressure sensor also exhibits a fast response–relaxation time,a low detection limit,excellent stability,which can be successfully used to measure human physiological signals.Lastly,an integrated sensor array system that can locate objects’positions is constructed and applied to simulate sitting posture monitoring.These results indicate that the proposed pressure sensor holds great potential in health monitoring and wearable electronic devices.

关键词： wearable pressure sensors multilayer structure high constant sensitivity multi-attribute physiological signals monitoring

Insights on high temperature friction mechanism of multilayer ta-C films

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Journal of Materials Science & Technology 2022年第2期97卷 29-37页

作者： Jing Wei Peng Guo Hao Li Peiling Ke Aiying Wang Key Laboratory of Marine Materials and Related Technologies Zhejiang Key Laboratory of Marine Materials and Protective TechnologiesNingbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China Ningbo Institute of Industrial Technology Ningbo 315201China

In this work,the high temperature friction mechanism of the tetrahedral amorphous carbon(ta-C)film was elucidated.The multilayer ta-C film with alternating hard and soft sub-layers exhibited a low friction coefficient of 0.14 at 400℃ before a sudden failure occurred at 4600 cycles.The wear failure was attributed to the gradual consumption of the ta-C film at the contact region.The design of a hard or soft top layer effectively regulated the high temperature friction properties of the multilayer ta-C.The addition of a hard top layer contributed to a low friction coefficient(0.11)and a minor wear rate(4.0×10^(-7)mm^(3)/(N m)),while a soft top layer deteriorated the lubrication effect.It was proposed that the passivation of dangling bonds at the sliding interface dominated the low-friction mechanism of the ta-C film at high temperature,while the friction induced graphitization and the formation of sp^(2)-rich carbonaceous transfer layer triggered C-C inter-film bonding,resulting in serious adhesion force and lubrication failure.Moreover,the multilayer ta-C film with hard top layer obtained excellent friction performance within 500℃,while the high temperature induced oxidation and volatilization of carbon atoms led to the wear failure at 600℃.

关键词： Tetrahedral amorphous carbon multilayer structure High temperature friction Wear mechanism

Long-term tribocorrosion resistance and failure tolerance of multilayer carbon-based coatings

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Friction 2022年第10期10卷 1707-1721页

作者： Hao LI Linlin LIU Peng GUO Lili SUN Jing WEI Yingrui LIU Shuyu LI Shuyuan WANG Kwang-Ryeol LEE Peiling KE Aiying WANG Key Laboratory of Marine Materials and Related Technologies Zhejiang Key Laboratory of Marine Materials and Protective TechnologiesNingbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China Computational Science Center Korea Institute of Science and TechnologySeoul 136-791Republic of Korea

Current tribocorrosion research of metallic materials and their surface protective coatings mainly focuses on their short-term properties,with test time of 0.5‒2.0 h and a sliding distance 50‒500 m,which may significantly deviate from the practical long-term service condition and thus cause a catastrophe of marine equipments.In this study,three carbon-based multilayer coatings(Ti/DLC,TiC_(x)/DLC,and Ti‒TiC_(x)/DLC)were deposited on S32750 substrates,and both short-term and long-term tribocorrosion behaviors were investigated.The experimental results indicate that the coatings substantially improve the tribocorrosion resistance of the S32750 stainless steel.During the short-term tribocorrosion test,TiC_(x)/DLC exhibited the best tribocorrosion resistance owing to its high hardness.During the long-term tribocorrosion test,however,Ti‒TiC_(x)/DLC coating indicated the best anti-tribocorrosion performance owing to its excellent fracture toughness together with high hardness.Moreover,under 5 N,Ti‒TiC_(x)/DLC can withstand a long-term test of more than 24 h.Additionally,under a higher load of 20 N,the Ti‒TiC_(x)/DLC with a corresponding sliding distance of approximately 1,728 m maintained a low friction coefficient of approximately 0.06.However,the coating was completely worn out;this is attributable to the formation of tribocorrosion products consisting of graphitized carbon and nanocrystalline Fe_(x)O_(y).

关键词： DLC multilayer structure long-term tribocorrosion failure tolerance

Multi-layer analytic solution for k-ωmodel equations via a symmetry approach

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Applied Mathematics and Mechanics(English Edition) 2023年第2期44卷 289-306页

作者： Fan TANG Weitao BI Zhensu SHE Department of Mechanics and Engineering Science College of EngineeringPeking UniversityBeijing 100871China State Key Laboratory for Turbulence and Complex Systems Peking UniversityBeijing 100871China

Despite being one of the oldest and most widely-used turbulence models in engineering computational fluid dynamics(CFD),the k-ωmodel has not been fully understood theoretically because of its high nonlinearity and complex model parameter setting.Here,a multi-layer analytic expression is postulated for two lengths(stress and kinetic energy lengths),yielding an analytic solution for the k-ωmodel equations in pipe flow.Approximate local balance equations are analyzed to determine the key parameters in the solution,which are shown to be rather close to the empirically-measured values from the numerical solution of the Wilcox k-ωmodel,and hence the analytic construction is fully validated.The results provide clear evidence that the k-ωmodel sets in it a multilayer structure,which is similar to but different,in some insignificant details,from the Navier-Stokes(N-S)turbulence.This finding explains why the k-ωmodel is so popular,especially in computing the near-wall flow.Finally,the analysis is extended to a newlyrefined k-ωmodel called the structural ensemble dynamics(SED)k-ωmodel,showing that the SED k-ωmodel has improved the multi-layer structure in the outer flow but preserved the setting of the k-ωmodel in the inner region.

关键词： turbulence model k-ωmodel structural ensemble dynamics(SED) multilayer structure symmetry

A modified single edge V-notched beam method for evaluating surface fracture toughness of thermal barrier coatings

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Applied Mathematics and Mechanics(English Edition) 2023年第5期44卷 693-710页

作者： Haoran BAI Zhanyu WANG Sangyu LUO Zhaoliang QU Daining FANG Institute of Advanced structure Technology Beijing Institute of TechnologyBeijing 100081China

The surface fracture toughness is an important mechanical parameter for studying the failure behavior of air plasma sprayed(APS)thermal barrier coatings(TBCs).As APS TBCs are typical multilayer porous ceramic materials,the direct applications of the traditional single edge notched beam(SENB)method that ignores those typical structural characters may cause errors.To measure the surface fracture toughness more accurately,the effects of multilayer and porous characters on the fracture toughness of APS TBCs should be considered.In this paper,a modified single edge V-notched beam(MSEVNB)method with typical structural characters is developed.According to the finite element analysis(FEA),the geometry factor of the multilayer structure is recalculated.Owing to the narrower V-notches,a more accurate critical fracture stress is obtained.Based on the Griffith energy balance,the reduction of the crack surface caused by micro-defects is corrected.The MSEVNB method can measure the surface fracture toughness more accurately than the SENB method.

关键词： thermal barrier coating(TBC) surface fracture toughness modified single edge V-notched beam(MSEVNB)method multilayer structure micro-defect

Oxidation behavior of Ni-based superalloy GH738 in static air between 800 and 1000℃

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Rare Metals 2021年第3期40卷 616-625页

作者： Jue Wang Hao Xue Ying Wang Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology Nanjing 211167China School of Materials Science and Engineering Nanjing Institute of TechnologyNanjing 211167China

The oxidation behavior of a nickel-based superalloy GH738 was studied by isothermal oxidation tests in still air at different temperatures,with exposure time up to 100 h.Oxidation-kinetic curves were plotted using the mass gain method.The surface and cross-sectional morphologies were observed by scanning electron microscopy(SEM).A composition analysis and an oxidation-product identification were conducted using energydispersive X-ray spectroscopy(EDS) and an X-ray diffraction(XRD),respectively.The results showed that GH738 exhibited parabolic oxidation-kinetic curves,with stable parabolic-rate constants at each temperatures.The activation energy of oxide growth was calculated to be329.6 kJ·mol^(-1).Cr_(2) O_(3)(chromia) was the external oxidation product at 800℃.A TiO_(2)-Cr_(2) O_(3) double-layer structure was formed at 900℃.The position of TiO_(2) changed from the oxide-metal interface to the air-oxide interface by the diffusion of Ti atoms in chromia during the oxidation time at this temperature.Spallation was observed in the Cr_(0.12)Ti_(0.78)O_(1.74)-Cr_(2) O_(3) multi-layer oxide of at 1000℃,which increased the oxidation rate.For all the tests,the main internal oxide was always Al_(2) O_(3).The entire GH738 oxidation process was interpreted by the competitive diffusion of elements(Cr,Ti,Ni,etc.) in metal matrix and chromia,while a schematic diagram of oxidation process was proposed.

关键词： GH738 Oxidation behavior Diffusion multilayer structure